Issues flying behind a 2-stroke

[akflyer 1427]

 

go drive a narrow WB jacked up car and haul ass into a corner and yank the wheel.  After you get out of the hospital go get one with a longer wheelbase  and wider stance and enjoy the ride..

A google search of the narrow gear versus wider gear on taildragger will probably get you more reading material than one evening worth of adult beverages will last.

 

[Allen Sutphin 705]

I try to think of the gear as trying to upset a wagon sideways. A narrow wagon isn't so tough to upset. A wide wagon is a little tougher. Don't know if this really applies, but it sure sounds good! You could probably dig out the old trig tables and prove or disprove this. Either way I can see a wider gear being more stable, but a higher gear, would seem to make it unstable. Either that or I don't know beans about high CG's. I know it will upset the apple cart, as mom used to say.

[wypaul 448]

Think in terms of pivot points and you will probably remember some HS physics as the light comes on.

I can tell you that my new wide and taller gear is capable of doing an emergency ground loop at 35 mph full right brake to keep from going into the creek after what would have been a 15' drop.  Both wheels stayed on the ground and the plane stopped facing the opposite direction with zero damage.  The plane pivoted around the right tire which I had locked the brakes on.  The gear uses the Roberts Rage system.  I can tell you I am sold on my wide gear setup.

Edited 16 Jan 2019 by wypaul

[Allen Sutphin 705]

Think in terms of pivot points and you will probably remember some HS physics as the light comes on.

 

All my light does is flicker anymore. I burnt it out in the early 70's figuring out that a Cobra gunship could haul 19 cases of stroh's beer. Especially with 4 19 tube rocket pods. Of course that was back when men were men and women were glad of it.

Edited 16 Jan 2019 by Allen Sutphin

[akflyer 1427]

Think in terms of pivot points and you will probably remember some HS physics as the light comes on.

 

All my light does is flicker anymore. I burnt it out in the early 70's figuring out that a Cobra gunship could haul 19 cases of stroh's beer. Especially with 4 19 tube rocket pods. Of course that was back when men were men and women were glad of it.

 

[Cloud Dancer 69]

slow RPM equals high EGT that's what kills them.

Are you referring to all 2 stroke engines or just Rotax? Plenty of people idle 2 strokes for extended periods of time without any adverse effects. I've got an old 1950's vintage outboard engine that's spent hours on end idling while trolling for fish in the lakes of Minnesota. It hardly ever fouls a plug either! And it has a much higher ratio of oil to gas than our Rotax 582's are burning. There's got to be a little more to the story.

[wypaul 448]

Turbo remember the big wide board you learned to windsurf on compared to to the little narrow board you now probably use.

[TJay 1041]

slow RPM equals high EGT that's what kills them.

Are you referring to all 2 stroke engines or just Rotax? Plenty of people idle 2 strokes for extended periods of time without any adverse effects. I've got an old 1950's vintage outboard engine that's spent hours on end idling while trolling for fish in the lakes of Minnesota. It hardly ever fouls a plug either! And it has a much higher ratio of oil to gas than our Rotax 582's are burning. There's got to be a little more to the story.

I was referring to 3500 rpm that's what Turbo was asking about. 3500 to 4500 is the worst thing for most 2 cycles.

[Cloud Dancer 69]

I said nothing about a cold seizure. 

 

The rotary valve only replaces reeds, has nothing to do with oiling at all.  The oil injection pump does that.  Yes it meters it at a lower feed rate, something to the tune of 50:1 wide open throttle and 70:1 at an idle IF you have the injection cable set right and its operating freely.  

The engine has 3 jets... idle jet, main jet and needle jet.  The needle and needle jet are what affect the cruise range of the engine.  Hence having in flight adjustable like the arctic sparrow needles or the hacman system that does it off the pressure in the bowl to keep EGTS in the optimum range and thereby having best fuel efficiency.

Of course the 2 stroke IS improved when going to fuel injection.  Not something that is reliably available for the rotax 582.

After going the route of attaching 02 sensors on sleds and dicking around with a boondocker box to tune the fuel injection most people learned expensive lessons and melted pistons.  Not only that, its another gauge to stare at and get lost in trying to tweedled in the best most efficient settings.  The engine is what it is, tune it to be good all around then keep your head out of the cockpit and pay attention to whats outside the windshield.  It is stupid easy to melt the pistons on a 2 stroke if you want to push the envelope.  On a sled you can do that and only have to tow it back to the truck or the trailer.  On a plane you run the risk of it being your last flight and I pray you don't take an innocent passenger with you.

I am off the soap box, I wont say anything more unless more incorrect information is posted.

 

I'm sorry, the cold seizure was in reply to Turbo's question earlier in this thread. Your right about the rotary valve replacing reed valves but I thought the same shaft on the rotary valve ran the oil pump thus controlling it?

Our 582's are obsolete so we won't see a magic box from Rotax to bolt on and adjust the air/fuel/oil ratio under all temperatures and altitudes and make them bullet proof.

The Boondocker boxes are like putting a faucet in front of your faucet to control the water mixture going into your bathtub. Any change in the first faucet throws off any mapping you have programed in and screws up your desired temperature. I think there are far too many variables to make this kind of an approach feasible by anyone.

Back to Turbo's original thoughts, I think they are valid under a given set of constraints. A light built, lightly loaded Avid Flyer at sea level on a cool day will probably fly with a Rotax 337 up front. The performance will stink but it will probably fly. Put a 582 Rotax on there under the same circumstances and you have about double the horsepower to play with. An inflight adjustable propeller that is properly designed to tax his airplane's performance envelope for take off and cruise speed should see a benefit.

Try that with a heavy airplane with an extremely heavy load in the mountain elevations on a hot density altitude day and the Inflight prop becomes a waste of time and money. You have already burned up any margin of extra manageable horsepower needed to make the inflight propeller feasible.

[Turbo 162]

C.D., I b'lieve you're onto something!  Based on my prop calculations, and the factory data, with my light, clean little bird, the shaft power required to fly level at low altitude is less than what the engine can produce at 3500 rpm.  Of course, I would need the IFA to pull it off.  And hopefully the prop efficiency won't tank at the higher pitch!  But the words of experience say I'd better not try to do it for long, or my engine will crud up.   Got to put the bit in her teeth at least every so often.  O.k. then!

[Turbo 162]

Turbo remember the big wide board you learned to windsurf on compared to to the little narrow board you now probably use.

Maybe that's the problem.  I taught myself to sail before the wide boards showed up.  I even had a speed needle for a while.  Not quite red-shift relativistic fast, but it was still scary fast, and lots of fun.  But that was before I moved to the Gorge and learned what fast really is. 

Seriously, though, I get the obvious benefits of a wide-track gear,  especially to be able to not damage your wings in a bad groundloop, but I am now convinced that it's the way the LG pivots about their attachment to the fuselage sides, with initially more outward motion of the tires than vertical motion, that is the major contributor to the narrower gear feeling squirrely.  Ironically, this same motion should make a tricycle-gear setup feel more benign and stable, but in either case, hard landings are sure to chew up your tires!

[akflyer 1427]

 

 

[Allen Sutphin 705]

As of now I only see two choices, either the standard gear or the wide gear of some variety since there are several versions available. I would guess each has to make their own choice and take into consideration where they fly and the conditions of that strip. Maybe add their ability into the mix. Highly experienced pro pilots still have ground loops so we can really never eliminate them. Some of these new(expensive) tailwheels say no ground loops, bullpucky, the chance will always be there, that's what keeps us on our toes, so to speak.

[Turbo 162]

slow RPM equals high EGT that's what kills them.

Are you referring to all 2 stroke engines or just Rotax? Plenty of people idle 2 strokes for extended periods of time without any adverse effects. I've got an old 1950's vintage outboard engine that's spent hours on end idling while trolling for fish in the lakes of Minnesota. It hardly ever fouls a plug either! And it has a much higher ratio of oil to gas than our Rotax 582's are burning. There's got to be a little more to the story.

I was referring to 3500 rpm that's what Turbo was asking about. 3500 to 4500 is the worst thing for most 2 cycles.

I've got to believe this is very dependent on the type and size of the engine.  Nobody else has contested the notion that these engines like to operate under load, and that their fuel efficiency is highest, and EGT lowest when loaded.  At 3500 rpm we are out of the gear-train resonance; we're out of that regime by 2500 rpm.  The 582 is liquid cooled, so kept warm by a thermostat, even if engine heat generation is way lower than the radiator can dissipate.  Leni's right that cabin heating may be insufficient for comfort.  Unless one's midrange needles are set up wrong, resulting in the engine running lean, I don't see anything damaging to the engine here, except perhaps in really cold conditions where even the thermostat can't keep the engine above the minimum coolant temp, causing crud to build up in the combustion chambers, and risking seisure.  Except for the very cold OAT case, I see little harm potential here.  I would think this would be very easy on the engine.

[Allen Sutphin 705]

I think it is easier on the engine but only as far as bearing wear, cylinder wear, fuel usage, etc. But carbon buildup is the biggest issue with low RPM, low heat operation. My Hirth is a high torque, low RPM engine designed to operate between 4000 and 5500 RPM. But it was designed for that and using the recommended oil, runs at 100/1 mix so a lot less carbon to start with. Don't advise anybody with a Rotax  to do it, but they weren't designed for a low RPM. If I was going to run at that RPM, then I think I'd use a pure syn oil so carbon isn't an issue. I don't have any issues with syn oil in my situation since the new syn oils are good for engine protection a lot better than years ago. Mine is stored in a dry barn when not flying, started weekly, and borescoped several times a year. One important thing, from an old A&P, if you are going to start it weekly or bi-weekly, make sure you reach operating temp or better yet, do a couple of high speed taxi's to get the temps up. Just starting it and idling for 10 minutes or so doesn't burn off any moisture and just gets it warm enough to create moisture inside the engine and exhaust. This will do damage! But this is based on my experience only and not from some engine company.

[Turbo 162]

Point taken.  I live in a high-humidity area, so have made the decision not to go with the true synthetic oils, like Amsoil Interceptor, despite their excellent lubrication performance.  My big concern is engine corrosion when the airplane is sitting, and from what I've read, in that regard I'm better off with more conventional "mineral" oils.  Locally, I can get a relatively inexpensive TC-W3 oil that's also rated API-TC, and is hence ashless, so that's what I'm going with.  Chris Bolkan reported good results with a similar oil type.  I'm hopeful that the oil injection system throttling the oil back to 70:1 at idle will spare me some crudding-up there.  

On cool days I have been able to hold (low) altitude at 4000 rpm, but I see that engine thermal efficiency peak of 34% at 3500 rpm, so am curious as to what I can get away with.  I suppose it's really more of an academic question, not particularly useful operationally.  But you're saying the new synthetics do a better job with rust protection than earlier versions?  Interesting.

Best of luck with that Hirth!  

[Allen Sutphin 705]

There is also semi-synthetics that are part dino oil and part synthetic and cover both bases. I wouldn't blend it myself due to proper formulas. You can't go wrong with TC-W3, its proven itself time and time again. Who knows, you might be on to something. We arrived at where we are today by people experimenting with non-standard ideas. Mistake or success, you will learn something new. Mine usually cost me just to learn what won't work. Been there, got the coffee mug, bumper sticker and T shirt, and a lot less money.

[Turbo 162]

Tell you what, fellas.  I'll only play this low-power game in the pattern or out in the flatlands, where the consequences of engine failure are mitigated.  No trees in sight.  Just harvested wheat fields.  And like I said, I'll put her "on the bit" once in a while just to keep it clean.  But first I'll see if I theoretically even have a big enough prop to make it work. Just a matter of a few well-thought-out runs thru my prop code.

[Allen Sutphin 705]

Sounds like you have a plan! Good Luck and we'll wait to hear the results. Just remember, the wheels stay on the bottom !

[akflyer 1427]

Learn something new every day.  I thought what set us apart from other mammals was the ability to learn from others mistakes.

In order to put enough pitch in at 3500 RPM and still maintain altitude your going to be lugging the poor engine in a big way.  2 stroke DO NOT like nor tolerate for very long LUGGING.  They do however give good service life when PROPERLY LOADED.  There are manufacture specs for a reason.  Loading an engine over that which gives proper static loading and stays within the parameters of maximum RPM is not the brightest idea.  The old 4 strokes and "conventional" aircraft engines are much more tolerant of pilot abuse than a 2 stroke.  There are a lot of smoking holes and statistics left by pilots who did not properly run their 2 stroke engines.  If you feel the burning desire to roll the dice and play with statistics please make sure the life insurance is paid up and your will is in order.

I don't want to sound like a dick, but what you are proposing to me sounds much more like a death wish than prudent experimentation and learning for the greater good of all man kind.

Do as ya wish but man... To prove you can do something for a few minutes is one thing, to think you can do it and get away with it for a long duration repeatedly just does not seem prudent to me.

The horror stories that you hear around the airports and on the net about how terrible the 2 smokes are and how dangerous they are seem to be perpetuated by people who refuse to pay attention and to run them outside the parameters.  

 

[Turbo 162]

I have no intention of operating the engine outside its specified operational parameters.  Any temp wanders outside the limits and it's experiment over.  Calculations so far indicate feasibility if the airframe (excluding prop, as a glider) has a best L/D of just over 8.  I remember being quoted 7:1 for a Cessna 150, but that is with a windmilling prop.  Take that prop out of the picture, and it's likely 10 or more.  I have already demonstrated level flight at low altitude at 4000 rpm, to no ill effect, with the prop pitch where it is.  Close to best L/D the power requirement is low, and the prop doesn't need to provide very much thrust.  In short, this is not lugging.  It's more like loafing.  Without the IFA, I'd need to take off with the pitch somewhat higher than it is now.  This means a longer takeoff roll and a flatter climb, at lower rate, but higher forward speed.  I already do this.  The feasibility can be estimated, and the goal approached incrementally, in recognition of the limitations inherent in my modelling of the prop's behavior with my code.  In the pursuit of cruise economy, I intend to map the tradeoff against climb rate anyway.  I am not proposing to fry my engine.  I'm an old guy, so I do things cautiously.  It's an experimental airplane.  Experimentation is expected, one would think.

[1avidflyer 1983]

I should keep my mouth shut, but I'll add this to the mix.  At between 5000-5200 rpm cruise I would burn about 3 1/2 gph with a 582.  Cruise with the Avid would be 70 - 75 MPH at those rpms.  If one can afford an airplane, the cost of 3 1/2 gph of flying fun is not very much.  If a guy switched to an HKS, you could probably get it down to 2 1/2 gph and save $3 or $4.  I like to save money as much as anyone, but the fuel is probably one of the smallest expenses involved in owning an airplane,  Just my 2 cents worth, YMMV  JImChuk

[Cloud Dancer 69]

Just back inside from blowing the first major snow off the sidewalks. I used an old Toro 2 stroke snow blower from the early 70's that I used as a kid when my grandfather purchased it new. Granted it only gets used a half dozen hours a year but it still amazes me it's still running. I've replaced parts over the decades but no work to the engine. It screams at full throttle and burns regular 30 weight oil mixed 1/2 pint per gallon. It never gets winterized but keeps on ticking like a Timex watch. Some might say I would be smart to run modern 2 cycle oil in it but I think I want to keep the 30 weight oil experiment running. Have we really gained anything with these new oils or are we just being sold snake oil?

I went to the Oshkosh air show a week early last year just to help assemble the WW1 birds Kermit Weeks had shipped up from Florida. I was amazed to learn they still use Castor oil in those engines. With all the advances in oil since WW1 and they stick with Castor oil. They told me they use it because it does not mix with fuel and therefore does not wash off the cylinder walls. The down side is it gets thick and gums up the engine during extended storage. Maybe it's because they are from Florida where it's warm, I don't know, but they have never heard of Sea Foam. I contacted a chemical engineer at Sea Foam and asked him about foaming rotary engines for storage. He said because it is mineral based like Castor oil it should work just fine. I forwarded the information to Kermit and he said he was going to look into it. Most people I know here in the Midwest winterize our two stroke water craft by fogging. There is even a fog port built into my jet ski just for this purpose. My snowmobiles got the same treatment for summer storage back when I sledded. I do know it keeps the  carbs from gumming up during storage. Before using it; every time I dug out the jet ski or snowmobile for the year, I would have to spend half a day taking carburetors apart and cleaning them to get the motors running smooth.

My question is when during engine development did we get away from Castor oil and why? Since you guys were talking oil, maybe someone has an answer. The only modern engines still using Castor oil that I can think of are those used for model aircraft, cars and boats and those are quickly being replaced with electric.

[Turbo 162]

From what I've read, castor oil's film strength can't be beat, even by the best synthetics, but it does eventually morph into a gummy residue.  I understand that certain types of off-road motorcycle racers still use it, since they disassemble at least part of the engine between races anyway.  Smells cool too!

[Turbo 162]

JimChuk, your point is well taken.  My bird is light and apparently clean, as I can easily top 80 mph at 5000 rpm, at low altitudes.  And I'm not tightly constrained economically, so I can afford the petrol, as well as the other stuff.  I suppose my fixation with minimum power stems from a desire to understand my bird's aerodynamic properties.  Hey, I'm a retired airplane aerodynamicist, what can I say?  Even this simple little putt-putt airplane is an object both magical and fascinating to me.  I also see it as a vehicle for a new class of adventures that I can share with my wife, that are exciting, yet not too strenuous for our old bodies.  This is in addition to serving as a testbed for various minor experiments.  True, I can't turn it into a map-gobbling rocketship, but that's o.k..  Its ability to fly is all the magic it needs, as far as I'm concerned.  It's the magnificent journey, not the boring destination!  I already live in my flavor of paradise.  Your kind words are always appreciated.

Edited 21 Jan 2019 by Turbo